[A case with rheumatoid arthritis complicated with ANCA-associated vasculitis]

A 50-year-old woman with rheumatoid arthritis (RA) developed constitutive symptoms such as fever and weight loss, mononeuritis multiplex and rapidly progressive glomerulonephritis (RPGN). The renal biopsy revealed crescentic glomerulonephritis (CrGN) with few immune deposits such as IgG and C 3 and necrotizing vasculitis, which led to the pathological diagnosis of microscopic polyangiitis (MPA). Moreover the high serum level of anti-myeloperoxidase (MPO) antibody, one of the anti-neutrophil cytoplasmic antibody (ANCA), suggested that she had ANCA-associated vasculitis. The renal prognosis of the ANCA-associated vasculitis is said to be poor unless patients were treated in the early phase of the disease. As we started to treat the patient when her serum creatinine level (sCr) was 1.7 mg/dl and creatinine clearance (CCr) was 27 ml/min, her renal function returned to the almost normal level (sCr = 0.6, CCr = 91). It is well known that patients with RA may develop various kinds of extraarticular manifestations which are usually related to immune-complex mediated vasculitis, what we call malignant RA. We emphasize that ANCA-associated vasculitis is another important complication of RA. When we see a RA patient with constitutional symptom, abnormal urinary sediments and other clinical signs of vasculitis such as mononeuritis multiplex, ANCA-associated vasculitis should be considered. Since the early diagnosis and treatment of ANCA-associated vasculitis is a key to prevent renal failure, it is encouraged to measure the serum ANCA titer for not only the diagnosis of such patients but the evaluation of their clinical course.